Hematuria and eosinophilia developed in two patients being treated for bacterial endocarditis with 20 or 24 gm/day of cephalexin given orally together with probenecid (Benemid). One patient had a concurrent transient increase in serum creatinine; both patients had a history of penicillin allergy and had previously received cephalexin intravenously. All abnormalities promptly remitted following discontinuation of therapy.